Variable phase shifter



May 3, 1949.

G. K. WERNER 2,469,188

VARIABLE PHASE SHIFTER Filed Feb. l, 1947 N su) IIIIII- E ewye. Il.Merfzef" Patented May 3, 19494 VARIABLE PHASE SHIFTER George K. Werner,Chicago, Ill., assignor to M-K Enterprises, Inc., Chicago, Ill., acorporation oi Illinois Application February 1, 1947, Serial No. 725,755

3 Claims. (Cl. 323-119) This invention relates to an electricalapparatus and particularly to a variable phase shifter adapted to varythe phase angle between two currents by any desired value for anydesired frequency while maintaining substantially constant amplitude.This invention is an improvement upon the phase shifter disclosed andclaimed in the copending application of William H. Bussey, Ser. No.725,764, and iiled together with this application.

Phase Shifters for producing a variable phase shift are well known andexist in a variety of forms. However, such Shifters as a rule arecharacterized by relative complexity and variable output and aresensitive to frequency variation. In addition, few Shifters are capableof varying the phase angle beyond ninety degrees. This inventionprovides a system which is relatively simple, economical, dependable,effective over any desired angular range to provide constant amplitudeand is independent of frequency; The invention, in general, provides aplurality of variable resistors, the variation in resistors and relativevalues being such that effective phase shift is provided.

For a more complete understanding of the invention, reference will nowbe made to the drawing wherein an exemplary embodiment is shown.

Leads I and Il are supplied with alternating current at any desiredfrequency' from which another current at a desired phase angle is to beobtained. Leads I0 and II are connected to leads I2 and I3 respectively.Leads I2 and I3 supply ninety degree phase shift means I5, it beingunderstood that the phase shift is xed. Inasmuch as means for obtaininga ninety degree phase shift are well known in the art, a detaileddescription thereof is deemed to be unnecessary. In general, such meanscomprise a combination of ca. pacitance and resistance, although othermeans are'well known. Phase shifter I5 supplies its output to leads I 8and I1.

Leads I2 and I3, on the one hand, and I8 and I1, on the other hand,supply currents at equal potentials to primaries lI 8 andl I9' oftransformers 23 and 20 respectively. The transformers have secondaries2| and 2|', each provided with center taps 22 and 22'. Secondaries 2|and 2l' have terminals 23 and 23', on the one hand, and 24 and 24', onthe other hand. Terminals 23 and 23' go to control grids 26 and 28' ofvacuum tubes 21 and 21 respectively. Similarly, terminals 24 and 24' areconnected to control grids 28 and 28' of vacuum tubes 28 and 28'respectively. Tubes 21 and 23 are arranged to form a push-pullampliiler. Similarly, tubes 21' and 29' are arranged for push-pulloperation. Vacuum tubes 21 and 23 have their cathodes 38 and 3|connected to ground through bias resistors 32 and 33. Center tap 22 isalso grounded. Similarly, vacuum tubes 21 and 29' have cathodes 30 and3|' connected through grounded bias resistors 32' and 33'. Center tap22' is also grounded. The cathode-bias resistors have a value high incomparison to normal cathode-bias resistors so that the vacuum tubefunctions substantially as a constant current device.

. Vacuum tube 21 has anode 33 connected to lwiper 34 cooperating withresistor 35. Resistor 35 has terminals 38 and 31 short-circuited by wire38. Wiper 34 is also connected through resistor to junction 4|.

Vacuum tube 29 has its anode 43 connected to wiper 44 cooperating withresistor 45, the resistor having terminals 48 and 41 short-circuited bywire 48. Wiper 44 is also connected through resistor 49 tov junction 4l.Shorting leads 38 and 48 are connected by wire 50 to a suitable anodesupply.

Vacuum tubes 21 and 28' are similarly connected to the correspondingprimed parts.

Resistors 35, 35', 45 and 45' are all wound in such a manner as tosubtend 180 deg-rees of arc. The resistors are so arranged that allwipers are similarly positioned in space and moved as a unit. Obviously,it is immaterial whether a wiper plays over the shorting lead, althougha continuous circuit from a wiper to a resistor terminal is necessary atall times. Thus, as shown, the wipers are pointing downwardly. Theresistors are staggered, resistors 35 and 45 being 180 degrees out ofphase. Similarly, resistors 35' and are each 180 degrees out of phasewith each other. Resistors 35 and 35 are 90 degrees out of phase withrespect to each other. All wipers are connected together to a commonactuating handle so that they may be turned simultaneously through equalangles... The wipers maintain contact with resistors or shorting leadsat all times.

It is understood that the resistors may be aligned in space, and thewipers displaced in phase.

In order to obtain desirable phase shifting, it is desirable thatresistors 35 or the corresponding other resistors be small in comparisonto the remaining resistors in the respective circuits. Thus, resistor 35should have a valuel small in comparison to load resistor 40. The sameapplies to resistors 35. 45 and 45' and their 3 respective circuit loadresistors l', 48 and I9'. It is understood that the potentials atterminals 23 and 2l, on the one hand, and terminals 23 and 2|', on theother hand, are equal although displaced in phase by 90 degrees.

The output of the system may be taken from junction 4| with respect toground and provide an alternating current whose phase with respect tothe currents in leads I0 and Il may be varied smoothly from zero through360 degrees while maintaining a substantially constant peak potential.The operation of the system is based upon the fact that ashort-circuited semi-circular resistor such as 35, when energized with asubstan tially constant current, will provide a potential variationwhose value closely approximates a sine function, the anglecorresponding to the sine being the angle of wiper 34 from a zeroposition. The zero position is shown by wiper 34 or 4I, this being atthe terminal of the resistor, although wiper 34 is effectively at zero.

It is understood, of course, that resistors 35,

45, and the primed resistors corresponding thereto may be disposed on astraight form and the wipers move in a straight line. It is easier,however, to consider the operation thereof in terms of circular arc.

While the outputs of the various resistors are shown as combined intoone output terminal 4I through the use of fixed resistors, it isunderstood that other means for combining potentials may be used. `Thus,wiper 34 and wiper 44, as one pair, may have their outputs combinedthrough resistors l0 and I9 as shown to provide one output terminalgoing to the input of a vacuum tube amplifier. Similarly, wipers 3l' and44 may have their outputs combined through resistors and 49' and thecombined outputs fed into the input circuit of another amplifier. Theoutputs of the two amplifiers may then be combined by connecting theanodes together. It is also possible to provide individual amplifiersfor each wiper and combine the amplified outputs in any one of severalwell-known manners, such as by transformers or the like.

What isclaimed is:

1.' A continuously variable phase shifter having a-substantiallyconstantamplitude at the output,

said shifter comprising a pair of vacuum tubes arranged to form a.push-pull amplifier and hav-v ing inputs and outputs, a short-circuitedresistor for eachv vacuum tube, a wiper cooperating with each resistorto form a potentiometer, means for connecting the output of each vacuumtube to the'wiper, a source of anode potential connected to theshort-circuited ends of each of said resistors, each short-circuitedresistor being disposed to provide a range of travel over which thecooperating wiper may move, said range of travel corresponding to 180degrees of arc, one potentiometer being arranged so that it is 180degrees ultaneously,

out of phase with the other, a second push-pull amplifier and pair ofshort-circuited resistors and cooperating wipers similarly arranged andconnected, the potentiometers oi' the first pushpull amplifier beingrespectively degrees out of phase with the potentiometers of the otherpushpull amplifier, means for moving all wipers simmeans for supplyingalternating potentials to the input of one push-pull amplifier, meansfor supplyingv similarv alternating potentials but 90 degrees out ofphase to the input of the other push-pull amplifier and means forcombining the potentials from the four wipers into one output potential.

2. A continuously variable phase shifter having a substantially constantamplitude at the output, said phase shifter comprising a' pair of vacuumtubes connected to form a push-pull amplifier, said amplifier having`input and output circuits respectively, a short-icircuited resistor in.the output circuit of each tube, each resistor subtending an angle ofdegrees, a wiper movable over the 180 degrees and contacting theresistor to form a potentiometer, a connection between a wiper andoutput of each tube, means for oper# ating each vacuum Atube in such amanner that the current through each tube and resistor is substantiallyconstant in all positions of the wiper, means for connecting a source ofanode potential to the terminals of said two resistors, means fordisposing said two potentiometers so that one is 180 degrees out ofphase with respect to the' other, a second push-pull system havingshort-circuited resistors and wipers arranged 180 degrees out of phasewith respect to each other, one potentiometer in the second group being90 degrees out of phase with respect to the potentiometers oi' the firstgroup, means for mechanically moving all wipers as a unit, means forcombining the potentials at the anodes of all tubes to form an outputpotential with reference to the common cathode connections, and meansfor energizing the two push-pull ampliers with .alternating currents 90degrees out' of phase with each other.

3. The system of claim 2 wherein said means for combining saidpotentials comprise resistors connecting the anode of eachl tube to theoutput terminal, said resistors having a value high in comparison to ashort-circuited resistor.v

GEORGE K. WERNER.

REFERENCES CIIV'ED The following references are of Vrecord in the fileof this patent: i

UNITED STATES PATENTS De Ryder Nov. 12,1945`

